Apparatus for controlling flow rate of gases used in semiconductor device by differential pressure

ABSTRACT

Provided is apparatus for controlling flow rate of gases used in semiconductor device by differential pressure by generating differential pressure in a fluid path. A differential pressure generation element generates pressure difference in the fluid path of gases used in semiconductor device fabrication, a pressure, sensor which is installed at a bypass of the fluid path detects the pressure difference, and a central processing unit (CPU) measures and controls a flow rate of the gases, thereby the present invention is capable of controlling the flow rate precisely and rapidly, and enhancing the degree of purity of the gases by the filtering function of the differential pressure generation element itself.

RELATED APPLICATIONS

The present application is based on International Application NumberPCT/KR04/001533, filed Jun. 24, 2004, and claims priority from, KoreanApplication Number 10-2003-0042584, filed Jun. 27, 2003, the disclosureof which is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to an apparatus for controlling flow rateof gases used in semiconductor device fabrication by differentialpressure, and more particularly, to an apparatus for controlling flowrate of gases used in semiconductor device fabrication by generatingdifferential pressure in a flow passage through which the gas flows.

BACKGROUND ART

As well known, semiconductor device fabrication employs gases such asdopant gas, etchant gas, diffusion gas and purge gas used formanufacturing semiconductor devices. The semiconductor devicefabrication requires that such gases have high purity. Further, the flowrates of the gases that determine characteristics of semiconductordevices should be precisely and rapidly controlled in semiconductordevice fabrication.

As an example of techniques for controlling the flow rate of a gas insemiconductor device fabrication, a heat sensitive type mass flow ratecontroller operates as follows. A gas flowing though a flow passage of abody of the controller is distributed at a predetermined ratio via abypass and then sent to a flow sensor. A thermal resistor of the flowsensor changes temperature by means of heat conduction according to thegas flow, a Wheatstone bridge detects the temperature change in thethermal resistor as a voltage change and outputs an electrical signal,and an amplifier amplifies the electrical signal from the Wheatstonebridge and inputs the amplified electrical signal into the controller.The controller compares the input electrical signal with a set point andopens or closes a control valve operated by a solenoid or thermalactuator based on the comparison results to control the flow rate of thegas.

However, the conventional heat sensitive type mass flow rate controllerhas a problem in that the flow rate of the gas is indirectly measured insuch a manner that the temperature of the thermal resistor of the flowsensor is changed by heat capacity according to the gas flow and thetemperature change in the thermal resistor is detected as the voltagechange by the Wheatstone bridge, resulting in very low response.Further, the conventional heat sensitive type mass flow rate controllerhas problems in that it does not ensure linearity of the relationshipbetween the flow rate and the electromotive force of the flow sensorthroughout the entire range of flow rate of the gas, and its reliabilityis greatly deteriorated due to changes in the sensitivity of the flowsensor according to gas pressure. Moreover, the conventional heatsensitive type mass flow rate controller has a problem in that it istroublesome to change a compensation constant for use in the measurementof the flow rate according to the kind of gas.

DISCLOSURE OF INVENTION

The present invention is conceived to solve the aforementioned problemsin the prior art. An object of the present invention is to provide anapparatus for controlling flow rate of gases used in semiconductordevice by differential pressure, wherein differential pressure isgenerated in the gas flowing through a flow passage and the flow rate ismeasured using the differential pressure of the gas, thereby greatlyimproving the response and reliability of the controller.

Another object of the present invention is to provide an apparatus forcontrolling flow rate of gases used in semiconductor device bydifferential pressure, wherein the flow rate of the gas can be preciselyand rapidly controlled due to a fast response speed of the controllerand a stable flow of the gas.

A further object of the present invention is to provide an apparatus forcontrolling flow rate of gases used in semiconductor device bydifferential pressure, wherein the controller can be manufactured andmaintained conveniently and economically due to its simple structure.

A still further object of the present invention is to provide anapparatus for controlling flow rate of gases used in semiconductordevice by differential pressure, wherein the degree of purity of the gascan be improved by means of a filtering function of a differentialpressure generation element itself that is installed in a flow passageand generates differential pressure in a flow of the gas.

According to the present invention for achieving the objects, there isprovided an apparatus for controlling flow rate of gases used insemiconductor device by differential pressure, which comprises a bodyhaving a flow passage for the gas used in the semiconductor devicefabrication, a control valve for controlling a flow of the gas byopening or closing the flow passage of the body, a differential pressuregeneration element installed in the flow passage of the body to generatedifferential pressure, a tube installed to penetrate through thedifferential pressure generation element, a pressure sensor received inthe tube to detect the differential pressure in the flow passagegenerated by the differential pressure generation element, and a centralprocessing unit for calculating the flow rate of the gas according to adetection signal input from the pressure sensor and controlling thecontrol valve.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view showing the configuration of a firstembodiment of an apparatus for controlling flow rate of gases used insemiconductor device by differential pressure according to the presentinvention.

FIG. 2 is a partially enlarged sectional view showing the configurationof the first embodiment of an apparatus for controlling flow rate ofgases used in semiconductor device by differential pressure according tothe present invention.

FIG. 3 is a sectional view taken along line III-III of FIG. 2.

FIG. 4 is a partially enlarged sectional view showing the configurationof a second embodiment of apparatus for controlling flow rate of gasesused in semiconductor device by differential pressure according to thepresent invention.

FIG. 5 is a sectional view taken along line V-V of FIG. 4.

FIG. 6 a partially enlarged sectional view showing the configuration ofa third embodiment of the apparatus for controlling flow rate of gasesused in semiconductor device by differential pressure according to thepresent invention.

FIG. 7 is a sectional view taken along line VII-VII of FIG. 6.

FIG. 8 a partially enlarged sectional view showing the configuration ofa fourth embodiment of the apparatus for controlling flow rate of gasesused in semiconductor device by differential pressure according to thepresent invention.

FIG. 9 is a sectional view taken along line IX-IX of FIG. 8.

BEST MODE FOR CARRYING OUT THE INVENTION

A first embodiment of an apparatus for controlling flow rate of gasesaccording to the present invention shown in FIGS. 1 to 3 will be firstdescribed. Referring to FIGS. 1 and 2, a body 10 defining the externalappearance of the apparatus for controlling flow rate of gases accordingto the present invention is formed with a flow passage 12 for gases suchas dopant, etchant, diffusion and purge gasses used in semiconductordevice fabrication. The flow passage 12 has a gas inlet 14 and a gasoutlet 16. The inlet 14 is connected to a gas supply device 18. The gasdischarged through the outlet 16 is supplied to a semiconductor devicefabrication process. An upstream portion of the flow passage 12 isconnected to a valve chamber 22 of a control valve 20. The valve chamber22 of the control valve 20 is provided with a valve body 26 for openingor closing the flow passage 12 by means of an operation of an actuator24 so as to control the flow of the gas. In this embodiment, theactuator 24 of the control valve 20 may comprise a solenoid.

Referring to FIGS. 1 to 3, the apparatus for controlling flow rate ofgases of the present invention has a differential pressure generationelement 30 installed at a downstream portion of the flow passage 12 togenerate differential pressure in the flow of the gas. The differentialpressure generation element 30 is formed of a porous material 32 forproducing resistance against the flow of the gas. The porous material 32comprises a ceramic filter or stainless steel filter having a pluralityof fine pores 34. The ceramic filter or stainless steel filter may bemade by means of sintering. Further, the stainless steel filter can bemade to have a surface with superior precision, cleanliness, chemicalstability, corrosion resistance and the like by means ofelectropolishing. Such a ceramic filter or stainless steel filter caneffectively adsorb and remove impurities contained in the gaspenetrating through the pores.

As specifically shown in FIG. 3, the apparatus for controlling flow rateof gases of the present invention has a tube 40 installed at an upperedge of the porous material 32 to penetrate therethrough along the flowdirection of the gas. A pressure sensor 50 for sensing pressure isreceived in a bore 42 of the tube 40. In this embodiment, the pressuresensor 50 is adapted to maintain a hermetic seal and may comprise adifferential pressure sensor for sensing differential pressure producedbetween upstream and downstream sides of the porous material 32.

As shown in FIGS. 1 and 2, the porous material 32 and the tube 40 areidentical with each other in length, and the pressure sensor 50 has alength shorter than that of the tube 40 and is received at one side ofthe tube 40. The lengths of the porous material 32, tube 40 and pressuresensor 50 may be changed properly, if necessary. The position of thepressure sensor 50 may be changed to any position within the tube 40.Although FIG. 3 shows that the tube 40 and the pressure sensor 50 haverectangular cross sections, the tube 40 and the pressure sensor 50 maybe formed to have circular cross sections.

Meanwhile, leads 52 of the pressure sensor 50 penetrate through the tube40, the porous material 32 and the body 10 and are then connected to acentral processing unit (CPU) 60. A detection signal of the pressuresensor 50 is inputted into the CPU 60. The CPU 60 operates the actuator24 of the control valve 20 according to the detection signal input fromthe pressure sensor 50 to open or close the flow passage 12, therebycontrolling the flow of the gas. The control valve 20 and the CPU 60 arereceived in a casing 70 that is detachably attached to the body 10.

In the apparatus for controlling flow rate of gases used insemiconductor device by differential pressure according to the presentinvention, the gas that is supplied from the gas supply device 18 whenthe valve body 26 of the control valve 20 is opened is introducedthrough the inlet 14 of the body 10 and then flows along the flowpassage 12 of the body 10 while sequentially passing through the valvechamber 22 and the pores 34 of the porous material 32. The pressure ofthe gas drops while the gas passes through the pores 34 of the porousmaterial 32, which have cross sectional areas narrower than that of theflow passage 12. Therefore, a pressure difference is produced betweenthe upstream and downstream sides of the porous material 32.

Then, the pressure sensor 50 received in the bore 42 of the tube 40detects the differential pressure produced between the upstream anddownstream sides of the porous material 32 and outputs the detectionsignal corresponding thereto. The CPU 60 compares the detection signalinput from the pressure sensor 50 with a set point and then obtains theflow rate of the gas. At this time, if the flow of the gas passingthrough the pores 34 of the porous material 32 is a laminar flow, thecorrelation between the detection signal of the pressure sensor 50 andan actual flow rate is linear. Thus, it is possible to greatly improveresponse to and reliability for the flow rate of the gas obtained by theCPU 60.

Further, the CPU 60 determines whether the flow rate of the gas obtainedis a predetermined proper flow rate. The CPU 60 also outputs a controlsignal for operating the actuator 24 of the control valve 20 to properlymaintain the flow rate of the gas. The valve body 26 opens or closes theflow passage 12 by means of the operation of the actuator 24 to controlthe flow of the gas.

Accordingly, the response characteristics and reliability can be greatlyimproved in such a manner that the pressure sensor 50 detects thedifferential pressure produced between the upstream and downstream sidesof the porous material 32, the CPU 60 calculates the flow rate of thegas, and the valve body 26 of the control valve 20 for opening orclosing the flow passage controls the flow rate of the gas. In addition,the flow rate of the gas can be precisely and rapidly controlled to beadapted to semiconductor device fabrication. The apparatus forcontrolling flow rate of gases of the present invention can bemanufactured conveniently and at a low cost using a simple structure inwhich the porous material 32 is installed in the flow passage 12 of thebody 10 and the pressure sensor 50 detects the differential pressure inthe gas due to the porous material 32. The porous material 32 and thepressure sensor 50 can be replaced easily and the maintenance thereofcan be made economically due to easy and convenient repairs. A trace ofimpurities contained in the gas passing through the pores 34 of theporous material 32 is adsorbed and removed by the pores 34, resulting ineffective improvement of the degree of purity of the gas.

FIGS. 4 and 5 show the configuration of a second embodiment of anapparatus for controlling flow rate of gases according to the presentinvention. The configuration and operation of the apparatus forcontrolling flow rate of gases according to the second embodiment issubstantially identical with those of the apparatus for controlling flowrate of gases according to the first embodiment described above.Referring to FIGS. 4 and 5, the porous material 32 is installed in theflow passage 12 of the body 10, and the tube 40 is installed at thecenter of the porous material 32 to penetrate therethrough along theflow direction of the gas. The leads 52 of the pressure sensor 50 arereceived in a bore 42 of the tube 40 and penetrate through the tube 40,the porous material 32 and the body 10 and are then connected to the CPU60 in the same manner as FIG. 1.

With the structure in which the tube 40 and the pressure sensor 50 areinstalled at the center of the porous material 32, the gas flows throughthe porous material 32 around the pressure sensor 50 disposed at thecenter of the flow passage 12. The pressure sensor 50 acts as a resistorfor producing resistance against the flow of the gas in the flow passage12 of the body 10. As shown in FIGS. 2 and 3, in the apparatus forcontrolling flow rate of gases according to the first embodiment inwhich the tube 40 and the pressure sensor 50 are in stalled at the upperedge of the porous material 32 to be in the vicinity of a wall surfaceof the flow passage 12, there are dead volumes upstream and downstreamof the contact portion of the pressure sensor 50 with an upper wallsurface of the flow passage 12 due to the pressure sensor 50 acting asthe resistor against the flow of the gas. In the apparatus forcontrolling flow rate of gases according to the second embodiment, theflow of the gas is established through the porous material 32 around thepressure sensor 50, thereby preventing the creation of such deadvolumes. Therefore, the apparatus for controlling flow rate of gasesaccording to the second embodiment has advantages in that the flow ofthe gas can be smoothly maintained and it has excellent response overthe apparatus for controlling flow rate of gases according to the firstembodiment.

FIGS. 6 and 7 show the configuration of a third embodiment of theapparatus for controlling flow rate of gases according to the presentinvention. The apparatus for controlling flow rate of gases according tothe third embodiment also comprises the body 10, the control valve 20,the CPU 60 and the casing 70 in the same manner as the apparatus forcontrolling flow rate of gases according to the first embodiment.Referring to FIGS. 6 and 7, a porous material 132 acting as thedifferential pressure generation element 30 is installed in the flowpassage 12 of the body 10, and the porous material 132 is formed of aceramic filter or stainless steel filter having a plurality of pores134.

The porous material 132 comprises a first vertical plate portion 136 avertically abutting on a lower wall surface of the flow passage 12, ahorizontal plate portion 136 b horizontally extending from a downstreamend of the first vertical plate portion 136 a, and a second verticalplate portion 136 c vertically extending from a downstream end of thehorizontal plate portion 136 b and abutting on the upper wall surface ofthe flow passage 12. The horizontal plate portion 136 b of the porousmaterial 132 is provided with a tube 140 therethrough vertically, i.e.perpendicularly to the flow direction of the gas. A pressure sensor 150is received in a bore 142 of the tube 140 in a hermetically sealedmanner. Leads 152 of the pressure sensor 150 penetrate through the tube140, the horizontal plate portion 136 b and the second vertical plateportion 136 c of the porous material 132, and the body 10 and are thenconnected to the CPU 60 in the same manner as FIG. 1.

In the apparatus for controlling flow rate of gases according to thethird embodiment constructed as above, the gas introduced through theinlet 14 of the body 10 flows along the flow passage 12 while passingthrough the respective pores 134 of the first and second vertical plateportions 136 a and 136 c. At this time, there is a drop in the pressureof the gas that has passed through the pores 134 having cross sectionalareas narrower than that of the flow passage 12, and a pressuredifference is produced between above and below the horizontal plateportion 136 b. The pressure sensor 150 received in the bore 142 of thetube 140 detects the differential pressure between above and below thehorizontal plate portion 136 b and outputs a detection signal. The CPU60 compares the detection signal input from the pressure sensor 150 witha set point, obtains the flow rate of the gas, and then controls theflow of the gas by opening or closing the flow passage 12 through theoperation of the actuator 24 of the control valve 20 in the same manneras described above.

Meanwhile, since the pressure sensor 150 is installed parallel with theflow direction of the gas in the apparatus for controlling flow rate ofgases according to the third embodiment shown in FIG. 6, the area of theface of the pressure sensor 150 viewed in the flow direction of the gasis greatly reduced as compared with the area of the face of the pressuresensor 50 shown in FIGS. 3 and 4. Such reduction in the area of the faceof the pressure sensor 150 results in reduction of a drag force ascompared with the pressure sensor 50. Accordingly, flow loss can beminimized.

FIGS. 8 and 9 show the configuration of a fourth embodiment of theapparatus for controlling flow rate of gases according to the presentinvention. The apparatus for controlling flow rate of gases according tothe fourth embodiment also comprises the body 10, the control valve 20,the CPU 60 and the casing 70 in the same manner as the apparatus forcontrolling flow rate of gases according to the first embodiment.Referring to FIGS. 8 and 9, a plurality of capillary tubes 36 as anotherexample of the differential pressure generation element 30 are installedin the flow passage 12 of the body 10 along the flow direction of thegas to produce resistance against the flow of the gas. Impuritiescontained in the gas passing through apertures 38 of the capillary tubes36 are adsorbed and removed by surfaces of the apertures 38. Thecapillary tubes 36 are made of a stainless steel material and thensubjected to electropolishing in the same manner as the porous material32 of the apparatus for controlling flow rate of gases according to thefirst embodiment. The capillary tubes 36 as the differential pressuregeneration element 30 may be substituted with a porous plate. Surfacesof the capillary tubes 36 or the porous plate may be coated with glass,if necessary.

Further, the tube 40 is installed at the center of each of the capillarytubes 36 along the flow direction of the gas, and the pressure sensor 50is installed in the bore 42 of the tube 40. In this embodiment, thecapillary tubes 36 and the tubes 40 may be constructed to be equal toeach other. In this case, the pressure sensor 50 may be installed in oneof the capillary tubes 36. The leads 52 of the pressure sensor 50penetrate through the capillary tubes 36 and the body 10 and are thenconnected to the CPU 60 in the same manner as FIG. 1.

Meanwhile, the pressure of the gas that has passed through the apertures38 of the capillary tubes 36 drops in the same manner as the porousmaterial 32 described above. The pressure sensor 50 detects differentialpressure between upstream and downstream sides of the capillary tubes 36and outputs a detection signal. The CPU 60 compares the detection signalinput from the pressure sensor 50 with a set point, obtains the flowrate of the gas, and then controls the flow of the gas by operating theactuator 24 of the control valve 20 in the same manner as describedabove. Impurities contained in the gas passing through the apertures 38of the capillary tubes 36 are adsorbed and removed by the inner surfacesof the apertures 38. Accordingly, the degree of purity of the gas can beeffectively improved.

The preferred embodiments of the present invention described above aremerely for illustrative purposes. The scope of the present invention isnot limited to the embodiments. Those skilled in the art can makevarious changes, modifications or substitutions within the technicalsprit and scope of the present invention defined by the appended claims.It should be understood that such embodiments fall within the scope ofthe present invention.

Further, although the present invention has been described in connectionwith control of the flow rate of a gas used in semiconductor devicefabrication, it can also be applied to control of the flow rate of a gasor other fluids used in a chemical process.

INDUSTRIAL APPLICABILITY

As described above, with the apparatus for controlling flow rate ofgases for control ling a gas used in semiconductor device fabricationaccording to the present invention, a differential pressure generationelement such as a porous material or capillary tubes is installed in aflow passage of the gas to generate differential pressure in the gasflowing along the flow passage, and the flow rate of the gas is measuredbased on the differential pressure in the gas, thereby greatly improvingresponse characteristics and reliability. Further, it is possible toprecisely and rapidly control the flow rate of the gas due to a fastresponse speed and stable flow of the gas. Moreover, there areadvantages in that manufacture and maintenance of the apparatus forcontrolling flow rate of gases can be made conveniently and economicallydue to its simple structure, and the degree of purity of the gas can beimproved by means of a filtering function of the differential pressuregeneration element itself that is installed in the flow passage andgenerates the differential pressure in the flow of the gas.

The invention claimed is:
 1. An apparatus for controlling flow rate of gases used in semiconductor device fabrication by differential pressure, comprising: a body having a flow passage for the gas used in the semiconductor device fabrication; a control valve for controlling a flow of the gas by opening or closing the flow passage of the body; a differential pressure generation element installed in the flow passage of the body to generate differential pressure; a tube installed to penetrate through the differential pressure generation element; a pressure sensor received in the tube to detect the differential pressure in the flow passage generated by the differential pressure generation element; and a central processing unit for calculating the flow rate of the gas according to a detection signal input from the pressure sensor and controlling the control valve.
 2. The apparatus as claimed in claim 1, wherein the differential pressure generation element comprises a porous material.
 3. The apparatus as claimed in claim 2, wherein the tube is installed to penetrate through the center of the porous material.
 4. The apparatus as claimed in claim 1, wherein the differential pressure generation element comprises a porous material having a first vertical plate portion vertically abutting on a lower wall surface of the flow passage, a horizontal plate portion horizontally extending from a downstream end of the first vertical plate portion, and a second vertical plate portion vertically extending from a downstream end of the horizontal plate portion and abutting on an upper wall surface of the flow passage.
 5. The apparatus as claimed in claim 4, wherein the tube is installed at the horizontal plate portion of the porous material to penetrate therethrough perpendicularly to a flow direction of the gas, and the pressure sensor is horizontally received in the tube.
 6. The apparatus as claimed in claim 1, wherein the differential pressure generation element comprises a plurality of capillary tubes installed along a flow direction of the gas. 